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Dead Battery Back To Life


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2003 996 C2 Cabriolet

Car has 3k miles. Battery dead - very little juice - barely enough to light the dash.

Live in NJ - temperature is in the 20's (F) - car is parked in a single car garage.

1. What is the best way to bring the OEM battery back to normal operation?

2. How concerned do I need to be about temperatures being below freezing - where as the manual says do not try and charge a frozen battery?

3. Do I need to remove the tops to the fuel cells?

4. Any thoughts on the Porsche Battery Maintainer? Heard there is a NEWER version - Porsche Battery Maintainer/Charge-O-Mat II? Any thoughts? Will these work to bring the battery back?

I am little skittish - don't want to fry anything - and I don't want to replace the battery.

Lookin' to be spoon-fed direction - want to get on this right away!

Thanks!

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How long does the car sit before the battery is dead.  Here in Chicago, we have had  temps between 0 -20 degrees for the past few weeks.  I hadn't started my car in almost 4 weeks and it fired up yesterday.  If your battery is going dead within a couple of weeks, either there is an accessory on, a short,  or just a bad battery.

Car has sat for more then 4 weeks - I think the cold was the final srtaw. Obvious I should have had a battery tender on it - so I think the battery is still viable - just sat too long.

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Stokes;

I have the "new" Porsche charger/maintainer. The older model was just a maintainer-not unlike the"Battery Tender" which has been around for years. Both plug into the cigarette lighter to feed voltage to the car-no clamping on the battery terminals required- no removing the battery cell caps.

They will recharge a partially discharged battery -often over days- and then 'maintain' the charge without overcharging or boiling the electrolyte out of the battery.

Less amperage than even a trickle charger-both will cycle themselves off and on when the battery is fully charged so there is no danger of overcharging.

A trickle charger will eventually ruin the battery if left on too long.

The 'maintainers' do not have a enough juice to start a car with a dead battery, nor do I think they will be able to recharge a fully discharged battery-at best that process with the 'maintainers' would take weeks.

The 'new' charger/maintainer has a switchable ( both manual and automatic) setting which when on "charge" (as noted by the 'empty' battery icon) will charge a fully discharged battery- it will then switch itself over to 'maintain' ( as noted by the 'half-empty' battery icon) the charge, and can be left plugged in indefinitely. It will then monitor the charge and switch itself between charge and maintain as the battery's voltage fluctuates.

A frozen battery indicates a full discharge- you have almost water in the cells. The plates will not be able to give back cations to the electrolyte and will overheat from the current supplied by the charger and be ruined or melt. In addition- since frozen liquid expands, you case could be cracked and any thawing will produce a nasty leak of electrolyte. Proceed with caution.

Regards,

BD

Edited by Bostonduce
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A battery that self discharges to a low state of charge begins an irreversible process of sulfation on the plates. Even after the battery is recharged the battery is permanently damaged. There will be less capacity available, less cold cranking amps and less ampere-hours available.

It is best to maintain the electrolyte level, especially in warmer temperatures and it is best to maintain the battery at or near fully charged, especially in warmer temperatures.

It does not hurt a battery to have a constant voltage of about 13.8 VDC applied indefinitely, to maintain the battery at 100% fully charged.

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It does not hurt a battery to have a constant voltage of about 13.8 VDC applied indefinitely, to maintain the battery at 100% fully charged.

I guess if your goal is to transform your car battery into a "dry" cell battery, you are correct. But if keep a constant 13.8 volts on the battery indefinitely, you will definately need a new one.

I don't know why some make such a big deal about the battery anyway. They cost <$50. If you start the car and run it for 30 minutes or more every 4 weeks, it should last 5 years or more. There is nothing special about the Porsche battery.

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A battery that self discharges to a low state of charge begins an irreversible process of sulfation on the plates. Even after the battery is recharged the battery is permanently damaged. There will be less capacity available, less cold cranking amps and less ampere-hours available.

It is best to maintain the electrolyte level, especially in warmer temperatures and it is best to maintain the battery at or near fully charged, especially in warmer temperatures.

It does not hurt a battery to have a constant voltage of about 13.8 VDC applied indefinitely, to maintain the battery at 100% fully charged.

It does not hurt a battery to have a constant voltage of about 13.8 VDC applied indefinitely, to maintain the battery at 100% fully charged.

I guess if your goal is to transform your car battery into a "dry" cell battery, you are correct.  But if keep a constant 13.8 volts on the battery indefinitely, you will definately need a new one.

According to battery manufacturers, maintaining a constant voltage charger, set at 13.8 VDC for a 12 V car battery, is a float charge, which may be maintained indefinately, as section 9.1.3 of this technical article shows. Sections 13. and 13.1 also contains information on long term charging and sulfation.
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